Thoughts about the design, and why civilian designers are intrigued by blended-wing-bodies too.
Now that the public has had its first glimpse of the B-21 Raider, let’s do some comparing and contrasting to civil concepts.
Not much can be said with certainty about the B-21, which is still at least four years from being introduced into service by the U.S. Air Force, with the first test flight scheduled sometime this year. The media was only allowed to view and photograph the test aircraft from the front during the Dec. 2 unveiling at Northrop Grumman’s plant in Palmdale, California.
But we know for sure that B-21 is a blended-wing-body, or BWB, meaning the wings and the main body of the aircraft are not clearly divided. We can easily see that in head-on shots of the B-21 and in the ample photos of its precursor, today’s B-2s. Both configurations resemble recent civil BWB designs, including Airbus’ MAVERIC*, a subscale flying model unveiled in 2020 at the Singapore Airshow, and the NASA-Boeing X-48B and C research aircraft. As similar as the military and civil concepts might look, their starting design principles are very different. B-21’s sleek shape is dictated by the need for minimal infrared and radar signatures. From the front view, one can tell that the engines are buried deeply in the fuselage. This conceals the motion of their fans and minimizes their exhaust signatures. The need to minimize the aircraft’s radar signature likely results in complex intake and exhaust designs, which at least partly explains why the Air Force and Northrop Grumman were so protective of the aft view during the unveiling. Burying the engines this way likely makes maintenance more of a chore, but stealth and survivability outweigh that consideration. Aerodynamic considerations are secondary but surely not neglected given that the B-21 must have a high combat radius, meaning the ability to fly far from its base in any direction. That spells a need for high fuel efficiency, and that comes from minimizing airframe drag, something a BWB shape does well.
Civil designers, by contrast, are attracted to BWB designs mainly for their interior roominess and the exterior real estate they provide for propulsion innovations. Without a need for stealth, engines can be mounted externally to improve their intake aerodynamics and simplify the maintenance. We see designs such as the European Union-funded AHEAD** concept that incorporates boundary layer ingestion technologies and NASA’s N3-X concept that distributes the propulsion around the airframe, including small electric fans positioned very close to the airframe, to draw in the slow-moving boundary layer air and improve propulsive efficiency. For a commercial aircraft, the fuel, passenger and cargo capacities amount to a crucial parameter. With the engines mounted externally, this parameter can be maximized. As for innovations, in announcing its plan to introduce hydrogen aircraft by 2035, Airbus two years ago presented a BWB concept as one of the candidates under its ZEROe design campaign. Will this be the way of the future? Probably not any time soon. During the 2022 Singapore Airshow, Chief Technical Officer Sabine Klauke called the concept “most futuristic” and said a more “classical” configuration would likely be the first hydrogen aircraft to market, according to Aviation Week.
is an associate professor at Amsterdam University of Applied Physics.